This invention relates to means for generating a voltage and is particularly although not exclusively applicable to machines in turbogenerator installations for providing a power supply for telemetry purposes.
It is necessary for the operation and testing of turbo-alternators to monitor a number of rotor conditions existing when the machine is operating in order to determine whether the machine is operating within its design parameters. Such conditions include temperature, strain and dimensional variation. It is well known to employ telemetry equipment for this purpose with sensing equipment mounted on the rotor providing signals to a stationary receiver.
A power supply is therefore required on the machine rotor to energise the telemetry transmitter. Known methods of providing such a supply include batteries, which must be designed to withstand the high rotational forces to which they are subjected and which have only a limited life span, sliprings which can be difficult to locate and are subject to wear, and inductive couplings which, by their nature, have to be closely coupled to provide adequate power transfer leading to fouling problems caused by vibration.